System For And Method Of Fast Pulse Gas Delivery

ABSTRACT

A system for delivering pulses of a desired mass of gas to a tool, comprising: a mass flow controller including flow sensor, a control valve and a dedicated controller configured and arranged to receive a recipe of a sequence of steps for opening and closing the control valve so as to deliver as sequence of gas pulses as a function of the recipe. The mass flow controller is configured and arranged so as to operate in either one of at least two modes: as a traditional mass flow controller (MFC) mode or in a pulse gas delivery (PGD) mode. Further, the mass flow controller includes an input configured to receive an input signal; an output configured to provide an output signal; a communication port configured to receive program instructions; memory configured and arranged to receive programming data determining the programmed configuration of the mass flow controller as either a digital or analog configuration; and a processor/controller for operating the mass flow controller in accordance with the programmed configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of copending U.S. patentapplication Ser. No. 14/209,216, entitled SYSTEM FOR AND METHOD OF FASTPULSE GAS DELIVERY, filed Mar. 13, 2014 in the names of Junhua Ding,Michael L'Bassi and Tseng-Chung Lee and assigned to the presentassignee; which is a continuation-in-part of copending U.S. patentapplication Ser. No. 13/344,387, entitled SYSTEM FOR AND METHOD OF FASTPULSE GAS DELIVERY, filed Jan. 5, 2012 in the names of Junhua Ding,Michael L'Bassi and Tseng-Chung Lee and assigned to the presentassignee; which claims priority from U.S. Provisional Patent ApplicationNo. 61/525,452, entitled SYSTEM AND METHOD OF FAST PULSE GAS DELIVERY,filed Aug. 19, 2011 in the names of Junhua Ding, Michael L'Bassi andTseng-Chung Lee and assigned to the present assignee; U.S. patentapplication Ser. No. 13/344,387 is also a continuation-in-part of U.S.patent application Ser. No. 13/035,534, entitled METHOD AND APPARATUSFOR MULTIPLE-CHANNEL PULSE GAS DELIVERY SYSTEM, filed Feb. 25, 2011 inthe name of Junhua Ding and assigned to the present assignee, now U.S.Pat. No. 9,348,339, issued May 24, 2016. The entire teachings of theabove applications are incorporated herein by reference.

BACKGROUND Field

This disclosure relates generally to mole or gas delivery devices, andmore particularly, to a method of and system for pulse gas delivery. Asused herein the term “gas(es)” includes the term “vapor(s)” should thetwo terms be considered different.

Overview

The manufacture or fabrication of semiconductor devices often requiresthe careful synchronization and precisely measured delivery of as manyas a dozen gases to a process tool. For purposes herein, the term“process tool” may or may not include a process chamber. Various recipesare used in the manufacturing process, involving many discrete processsteps, where a semiconductor device is typically cleaned, polished,oxidized, masked, etched, doped, metalized, etc. The steps used, theirparticular sequence, and the materials involved all contribute to themaking of particular devices.

As device sizes have shrunk below 90 nm, one technique known as atomiclayer deposition, or ALD, continues to be required for a variety ofapplications, such as the deposition of barriers for copperinterconnects, the creation of tungsten nucleation layers, and theproduction of highly conducting dielectrics. In the ALD process, two ormore precursor gases are delivered in pulses and flow over a wafersurface in a process tool maintained under vacuum. The two or moreprecursor gases flow in an alternating or sequential manner so that thegases can react with the sites or functional groups on the wafersurface. When all of the available sites are saturated from one of theprecursor gases (e.g., gas A), the reaction stops and a purge gas isused to purge the excess precursor molecules from the process tool. Theprocess is repeated, as the next precursor gas (i.e., gas B) flows overthe wafer surface. For a process involving two precursor gases, a cyclecan be defined as one pulse of precursor A, purge, one pulse ofprecursor B, and purge. A cycle can include the pulses of additionalprecursor gases, as well as repeats of a precursor gas, with the use ofa purge gas in between successive pulses of precursor gases. Thissequence is repeated until a final geometric characteristic, such asthickness, is reached. These sequential, self-limiting surface reactionsresult in one monolayer of deposited film per cycle.

The delivery of pulses of precursor gases introduced into a process toolcan be controlled using a pulse gas delivery (PGD) device (thecontrolled flow of gas into and out of a delivery chamber using inletand outlet on/off-type valves simply by timing the opening of the outletshutoff valve for a predetermined period of time to deliver a desiredamount (mass), in the form of a pulse, of precursor gas into the processchamber of the process tool). Alternatively, a mass flow controller(“MFC”), which is a self-contained device comprising a transducer,control valve, and control and signal-processing electronics, has beenused to deliver an amount of gas at predetermined and repeatable flowrates, in short time intervals.

Pulse gas delivery (PGD) devices are usually pressure based andoptimized to provide repeatable and precise quantities (mass) of gasesfor use in semiconductor manufacturing processes, such as ALD processes.Typically, as shown in FIG. 1, current PGD devices include a deliverygas chamber 12, an inlet shut off valve 14 for controlling the flow ofgas from a gas supply 52 into chamber 12, and an outlet shut off valve16 for controlling the flow of gas from the delivery chamber 12 to theprocess tool 54. A host controller or computer 50 runs the gas deliveryprocess as well as carries out all of the control and diagnosticfunctions for the process tool, including, for example, safetymonitoring and control, RF power signals, and other common tasks. Sincethe volume of the delivery chamber 12 is fixed and known, the amount ofgas, measured in moles, introduced into the delivery chamber with eachpulse is a function of the gas type, the temperature of the gas in thechamber, and the pressure drop of the gas during the duration of thepulse delivered from the chamber 12. Accordingly, pressure sensor 18 andtemperature sensor 20 provide measurements of the pressure andtemperature to the controller 24 so that the gas delivered from thechamber during each pulse can be determined. The control logic forrunning the PGD device has thus been traditionally and typically on thehost controller 50 associated with the process tool. Improvements aredescribed in the copending Applications by providing a dedicatedcontroller 24 for separately controlling the pulse delivery process byoperation of the inlet and outlet valves 14 and 16.

More recently, certain processes have been developed that require highspeed pulsed or time-multiplexed processing. For example, thesemiconductor industry is developing advanced, 3-D integrated circuitsthru-silicon vias (TSVs) to provide interconnect capability fordie-to-die and wafer-to-wafer stacking. Manufacturers are currentlyconsidering a wide variety of 3-D integration schemes that present anequally broad range of TSV etch requirements. Plasma etch technologysuch as the Bosch process, which has been used extensively for deepsilicon etching in memory devices and MEMS production, is well suitedfor TSV creation. The Bosch process, also known as a high speed pulsedor time-multiplexed etching, alternates repeatedly between two modes toachieve nearly vertical structures using SF₆ and the deposition of achemically inert passivation layer using C₄F₈. Targets for TSV requiredfor commercial success are adequate functionality, low cost, and provenreliability.

These high speed processes require fast response times during thetransition time of the pulses in order to better control the processes,making the use of pressure based pulse gas delivery devices problematic.Currently, one approach to increase response time is to use a fastresponse mass flow controller (MFC) to turn on and off gas flows of thedelivery pulse gases delivered to the process tool according to signalsreceived from a host controller. The repeatability and accuracy of pulsedelivery using a fast response MFC with a host controller, however,leaves room for improvement, because response times are dependent on theworkload of the host controller. The host controller may be preventedfrom sending timely control signals if it is performing other functionsthat require its attention. Further, with short duration control signalsbeing sent from the host controller to the mass flow controller,communication jitter can occur, causing errors in the delivery of pulsesof gas. Workload of the host controller and communication jitter are twosources of error that reduce the repeatability and accuracy of pulse gasdelivery when relying on fast communication between the host controllerand the mass flow controller delivering pulses of gas.

Description of Related Art

Examples of pulse mass flow delivery systems can be found in U.S. Pat.Nos. 7,615,120; 7,615,120; 7,628,860; 7,628,861, 7,662,233; 7,735,452and 7,794,544; U.S. Patent Publication Nos. 2006/0060139; and2006/0130755, and pending U.S. application Ser. Nos. 12/689,961,entitled CONTROL FOR AND METHOD OF PULSED GAS DELIVERY, filed Jan. 19,2010 in the name of Paul Meneghini and assigned the present assignee;and U.S. patent application Ser. No. 12/893,554, entitled SYSTEM FOR ANDMETHOD OF FAST PULSE GAS DELIVERY, filed Sep. 29, 2010 in the name ofJunhua Ding, and assigned to the present assignee; and U.S. patentapplication Ser. No. 13/035,534, entitled METHOD AND APPARATUS FORMULTIPLE-CHANNEL PULSE GAS DELIVERY SYSTEM, filed Feb. 25, 2011 in thename of Junhua Ding and assigned to the present assignee.

SUMMARY

As discussed above, workload of a host controller and communicationjitter reduce the repeatability and accuracy of pulse gas delivery.Hence, by reducing the workload of the host controller and movingcontrol signals from the host to the controller of the MFC, these twofactors are reduced, resulting in improved repeatability and accuracy ofthe gas pulse delivery.

In one embodiment, a programmable mass flow controller comprising: aninput configured to receive an input signal and an output configured toprovide an output signal. A communication port is configured to receiveprogram instructions including instructions relating to the programmedconfiguration of the mass flow controller, and programming data. A flowsensor is configured to sense the flow of gas through the mass flowcontroller; and a control valve is configured to control the flow of gasthough the mass flow controller. Memory is configured and arranged toreceive programming data determining the programmed configuration of themass flow controller as either a digital or analog configuration; and aprocessor/controller is providing to operate the mass flow controller inaccordance with the programmed configuration.

In one embodiment the programmed digital configuration enables the massflow controller to respond to digital signals applied to the input. Inone embodiment the programmed analog configuration enables the mass flowcontroller to respond to analog signals applied to the input. In oneembodiment the communication port also is configured to receive datarelating to parameters associated with at least one of two modes ofoperation of the mass flow controller. In one embodiment the at leastone of two modes of operation of the mass flow controller includes aclassic mass flow controller mode of operation, wherein the input signalrepresents the flow setpoint for operating the MFC in the classic massflow controller mode of operation. In one embodiment the at least one oftwo modes of operation of the mass flow controller includes a pulse gasdelivery mode of operation, wherein the input signal represents a pulsetrigger signal for operating the MFC so as to deliver a sequence ofpulses in the pulse gas delivery mode of operation. In one embodimentthe communication port is configured to receive parameters for pulse gasdelivery. In one embodiment the parameters are associated with a moledelivery mode of gas pulse delivery operation. In one embodiment theparameters include the pulse-on period, pulse-off period, the moledelivery setpoint, and the number of pulses. In one embodiment the massflow controller further includes a digital communication interface thatincludes the digital communication port. In one embodiment the mass flowcontroller further includes an analog communication interface having ananalog input pin for forming the input and receiving an analog triggersignal input, and an analog output pin for forming the output andproviding an analog synchronization signal output. In one embodiment themass flow controller further includes both a digital communicationinterface and an analog communication interface. In one embodiment theoutput signal represents a synchronization signal for use insynchronizing the timing of the delivery of a sequence of pulses withthe operation of another device. In one embodiment the another device isa second mass flow controller. In one embodiment the synchronizationsignal is a trigger signal input to the second mass flow controller. Inone embodiment the another device is an RF power generator. In oneembodiment the another device is a pressure controller. In oneembodiment the synchronization signal is generated prior to thecompletion of the delivery of the sequence of pulses. In one embodimentthe synchronization signal is generated simultaneously with thecompletion of the delivery of the sequence of pulses. In one embodimentthe synchronization signal is generated after the completion of thedelivery of the sequence of pulses by a predetermined delay. In oneembodiment the pulse trigger signal is a digital signal. In oneembodiment the pulse trigger signal is an analog signal. In oneembodiment the output signal is a TTL synchronization output signal foruse by another device.

In one embodiment a system comprises: a multi-channel gas deliverysystem including a plurality of flow channels, each channel comprising amass flow controller configured to control the flow of gas through thecorresponding channel. Each mass flow controller includes: an inputconfigured to receive an input signal; an output configured to providean output signal; a communication port configured to receive programinstructions including instructions on the operational configuration ofeach mass flow controller; a flow sensor configured to sense the flow ofgas through the mass flow controller of the corresponding channel; acontrol valve configured to control the flow of gas though the mass flowcontroller of the corresponding channel; memory configured and arrangedto receive programming data determining the programmed configuration ofthe mass flow controller as either a digital or analog configuration;and a processor/controller for operating the mass flow controller inaccordance with the programmed configuration. The input signal to themass flow controller initiates the operation of the mass flow controllerto deliver a prescribed amount of gas, and the output signal isgenerated as a function of the timing of the delivery so that the outputsignal can be used to synchronize each mass flow controller to at leastone other device.

In one embodiment the output signal of at least one mass flow controlleris used as an input signal to initiate the operation of another one ofthe mass flow controllers of the multi-channel fast pulse gas deliverysystem to deliver a prescribed amount of gas so that the mass flowcontrollers define a daisy chain of devices sequentially providing thedelivery of prescribed amounts of gas through the correspondingchannels.

In one embodiment the output signal of each of the mass flow controllersis used to provide control signals applied to an RF power generator. Inone embodiment the output signal of each of the mass flow controllers isused to provide control signals applied to a pressure controller. In oneembodiment the input and output signals are analog signals. In oneembodiment the digital communication port of each mass flow controlleris configured to receive data relating to parameters associated with atleast one of two modes of operation of the mass flow controller. In oneembodiment the at least one of two modes of operation of each mass flowcontroller includes a pulse gas delivery mode of operation, wherein theinput signal represents a pulse trigger signal for operating the MFC soas to deliver a sequence of pulses in the pulse gas delivery mode ofoperation. In one embodiment the digital communication port isconfigured to receive parameters for pulse gas delivery. In oneembodiment the parameters are associated with a mole delivery mode ofgas pulse delivery operation. In one embodiment the parameters includethe pulse-on period, pulse-off period, the mole delivery setpoint, andthe number of pulses. In one embodiment the system further includes adigital communication interface that includes the digital communicationport. In one embodiment the system further includes both a digitalcommunication interface and an analog communication interface. In oneembodiment the system further includes an analog communication interfacehaving an analog input pin for forming the input and receiving an analogtrigger signal input, and an analog output pin for forming the outputand providing an analog synchronization signal output. In one embodimentthe analog synchronization signal is generated prior to the completionof the delivery of the sequence of pulses. In one embodiment the analogsynchronization signal is generated simultaneously with the completionof the delivery of the sequence of pulses. In one embodiment the analogsynchronization signal is generated after the completion of the deliveryof the sequence of pulses by a predetermined delay. In one embodimentthe output signal is a TTL synchronization output signal for use byanother device.

In one embodiment a method of operating a mass flow controller of thetype comprising at least one communication port, comprises: receiving,at the communication port, program instructions including instructionsrelating to the operational configuration of the mass flow controller asresponsive to either digital or analog input signals; and operating themass flow controller in accordance with the programmed configuration.

In one embodiment a programmed digital operational configuration enablesthe mass flow controller to respond to digital signals applied to theinput. In one embodiment a programmed analog operational configurationenables the mass flow controller to respond to analog signals applied tothe input. In one embodiment receiving at the communication port programinstructions includes receiving data relating to parameters associatedwith at least one of two modes of operation of the mass flow controller.In one embodiment at least one of two modes of operation of the massflow controller includes a classic mass flow controller mode ofoperation, and the input signal represents the set point setting foroperating the MFC in the classic mass flow controller mode of operation.In one embodiment at least one of two modes of operation of the massflow controller includes a pulse gas delivery mode of operation, andfurther delivering a sequence of pulses in the pulse gas delivery modeof operation in response to an input signal. In one embodiment receivinginstructions at the communication port program includes receivingparameters for pulse gas delivery. In one embodiment the parameters forpulse gas delivery are associated with a mole delivery mode of gas pulsedelivery operation. In one embodiment the parameters include thepulse-on period, pulse-off period, the mole delivery setpoint, and thenumber of pulses. In one embodiment the method further includesreceiving an analog trigger signal input at an analog input pin of ananalog communication interface and providing an analog synchronizationsignal output at an analog output pin of the analog communicationinterface. In one embodiment the method further includes generating anoutput signal representing a synchronization signal for use insynchronizing the timing of the delivery of a sequence of pulses withthe operation of another device. In one embodiment the another device isa second mass flow controller. In one embodiment the synchronizationsignal is a trigger signal for use as an input to the second mass flowcontroller. In one embodiment the another device is an RF powergenerator. In one embodiment the another device is a pressurecontroller. In one embodiment the method further includes generating thesynchronization signal prior to the completion of the delivery of thesequence of pulses. In one embodiment the method further includesgenerating the synchronization signal simultaneously with the completionof the delivery of the sequence of pulses. In one embodiment the methodfurther includes generating the synchronization signal by apredetermined delay after the completion of the delivery of the sequenceof pulses. In one embodiment the trigger signal is generated as adigital signal. In one embodiment the trigger signal is generated as ananalog signal. In one embodiment the output signal is a TTLsynchronization output signal for use by another device.

In one embodiment a method of operating a multi-channel gas deliverysystem including a plurality of flow channels is provided. Each channelcomprises a mass flow controller configured to control the flow of gasthrough the corresponding channel. The method comprises: providing aninput signal to one of the mass flow controllers so as to initiate theoperation of the mass flow controller to deliver a prescribed amount ofgas; generating an output signal from the mass flow controller as afunction of the timing of the delivery of the prescribed amount of gasso that the output signal can be used to synchronize each mass flowcontroller to at least one other device; receiving program instructionsat a communication port including instructions on the operationalconfiguration of each mass flow controller; determining the programmedconfiguration of the mass flow controller as either a digital or analogconfiguration as a function of the received instructions; and operatingthe mass flow controller in accordance with the programmedconfiguration. The input signal to the mass flow controller initiatesthe operation of the mass flow controller to deliver a prescribed amountof gas, and the output signal is generated as a function of the timingof the delivery so that the output signal can be used to synchronizeeach mass flow controller to at least one other device.

In one embodiment method further includes using the output signal of atleast one mass flow controller as an input signal to initiate theoperation of another one of the mass flow controllers of themulti-channel fast pulse gas delivery system to deliver a prescribedamount of gas so that the mass flow controllers define a daisy chain ofdevices sequentially providing the delivery of prescribed amounts of gasthrough the corresponding channels. In one embodiment the method furtherincludes applying the output signal of each of the mass flow controllersas a control signal to an RF power generator. In one embodiment themethod includes applying the output signal of each of the mass flowcontrollers as a control signal to a pressure controller. In oneembodiment the input and output signals are analog signals. In oneembodiment the method further includes receiving at a digitalcommunication port of each mass flow controller data relating toparameters associated with at least one of two modes of operation ofeach such mass flow controller. In one embodiment the at least one oftwo modes of operation of each mass flow controller includes a pulse gasdelivery mode of operation, wherein the input signal represents a pulsetrigger signal for operating the MFC so as to deliver a sequence ofpulses in the pulse gas delivery mode of operation. In one embodimentreceiving at a digital communication port of each mass flow controllerdata relating to parameters associated with at least one of two modes ofoperation of each such mass flow controller includes receivingparameters for pulse gas delivery. In one embodiment receiving at adigital communication port of each mass flow controller data relating toparameters associated with at least one of two modes of operation ofeach such mass flow controller includes receiving parameters associatedwith a mole delivery mode of gas pulse delivery operation. In oneembodiment the parameters include the pulse-on period, pulse-off period,the mole delivery setpoint, and the number of pulses. In one embodimentthe output signal of each mass flow controller is an analogsynchronization signal, and further including generating the analogsynchronization signal prior to the completion of the delivery of thesequence of pulses by the mass flow controller. In one embodiment theanalog synchronization signal is generated simultaneously with thecompletion of the delivery of the sequence of pulses. In one embodimentthe analog synchronization signal is generated after the completion ofthe delivery of the sequence of pulses by a predetermined delay. In oneembodiment the output signal of each mass flow controller is a TTLsynchronization output signal for use by another device.

These, as well as other components, steps, features, objects, benefits,and advantages, will now become clear from a review of the followingdetailed description of illustrative embodiments and the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

The drawings disclose illustrative embodiments. They do not set forthall embodiments. Other embodiments may be used in addition or instead.Details which may be apparent or unnecessary may be omitted to savespace or for more effective illustration. Conversely, some embodimentsmay be practiced without all of the details which are disclosed. Whenthe same numeral appears in different drawings, it refers to the same orlike components or steps.

FIG. 1 is a block diagram of a prior art gas delivery system forproviding high speed pulse delivery;

FIG. 2 are graphical representations of a test gas pulse illustratingthe flow rate over time;

FIG. 3 is an embodiment of a gas delivery system using a highperformance MFC and modified according to the teachings describedherein;

FIG. 4 illustrates a typical time based pulse gas delivery profiledownloaded to the MFC so that the MFC can deliver a series of gas pulseswithout the need to interact with the host controller, and thus operatefreely of the host controller overhead functions;

FIGS. 5A and 5B are examples of sets of profiles of M pulses forconfiguring the MFC controller so that the MFC controller canautomatically deliver, in response to a trigger signal from the hostcontroller, the M-pulse profile by turning on and off itself so as togenerate the pulses in the sequence dictated by the recipe downloaded bythe host computer;

FIG. 6 is a simplified block diagram of one embodiment of an electronicsystem of a mass flow controller;

FIG. 7 is a block diagram of one embodiment of a system arrangementincluding a host computer and a plurality of connected high performancemass flow controllers;

FIG. 8 is a timing diagram illustrating an example of theinterrelationship of the operation of the mass flow controllers shown inFIG. 7; and

FIG. 9 is a typical flow control diagram of one embodiment of a massflow controller such as the one illustrated in FIG. 6, used in thesystem of FIG. 7.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments are now discussed. Other embodiments may beused in addition or instead. Details which may be apparent orunnecessary may be omitted to save space or for a more effectivepresentation. Conversely, some embodiments may be practiced without allof the details which are disclosed.

An experiment was conducted using a test set-up for analyzing fast gaspulse delivery using a fast response MFC controlled by a host computerin order to illustrate the steepness of the transient edges of eachpulse of gas delivered from the MFC as a measure of the response of theMFC going from zero flow to full flow and from full flow to zero flow.Each pulse of gas delivered by the MFC was controlled with a hostcomputer, which included a sequence of delivery steps typical of arecipe. One pulse produced by a fast response MFC during the deliveryphase is shown in FIG. 2. As shown the transient edges of the gas pulse(flow rate vs. time) is fairly steep indicating quick response times ofthe control valve of the MFC. In analyzing the results of theexperiment, however, the performance suffered making the systemunreliable for high speed processes such as the Bosch process.

More specifically, the experiment used a mass flow verifier to measurethe amount of gas delivered from a fast response MFC controlled by ahost computer, and data was generated to determine the repeatability ofthe system. The pulses of gas that were delivered by the MFC sufferedfrom repeatability errors because of the variations in the timing of theresponse of the MFC to each pulse relative to the timing of the responseto the previous pulse, i.e., repeatability errors with respect to theresponse of the MFC to a command from the host computer to provide apulse varying from when it should occur based on the timing of theprevious pulse and the time that it actually occurred. It was determinedthat among the causes for this error is the already high demand for thehost controller's resources. Although a host controller may queue anon/off signal to be sent to the MFC, the signal may not be sentimmediately, depending on the work load of the host controller at thatmoment. Similarly, even when an on/off signal is transmitted,communication jitter between the host controller and the MFC caused by ashort and/or fast pulse width degrades the performance of the pulse gasdelivery, including repeatable and accurate performance. The relativetiming of pulses is crucial to the success of many high speed pulsedelivery applications. Thus, it is desirable to provide a solution forhigh speed pulse delivery applications, such as the Bosch process usedfor TSV creation, that reduces or overcomes these problems.

Referring to FIG. 3, one embodiment of a high performance MFC 160 usefulin controlling a high speed pulse delivery application is configured tobe connected between a source of gas 140 and a processing tool 200 andto receive a series of instructions from a user interface/hostcontroller 150 so as to provide a series of pulses of source gas toprocessing tool 200. High performance mass flow controller (MFC) 160,such as a πMFC manufactured and sold by the present assignee, includes aflow sensor 170 and an adjustable control valve 190. The sensor 170senses the mass flow through the sensor, and provides a signalrepresentative of the measured flow to the dedicated MFC controller 180.The dedicated controller 180 compares the measured flow with a flow setpoint so as to provide a control signal used to control the adjustablecontrol valve 190 so that the output flow of the valve to the processtool 200, such as a process chamber, is maintained at the set pointvalue.

In one embodiment according to the present disclosure, the MFC 160 hastwo modes of operation, providing one significant advantage overpressure based pulse gas delivery devices. A first mode is a traditionalmass flow controller (MFC) mode, where a host controller 150 sends flowset point signals to the MFC 160 to control the flow delivered to theprocessing tool 200. A second mode is a pulse gas delivery (PGD) mode.In PGD delivery processes, MFC 160 is arranged to receive the pulseprofile and the necessary profile and sequencing of pulses so that theMFC can deliver a gas from the supply 140 to the chamber 200 inaccordance with a recipe including a profile and sequence of timedpulses provided by the user. The profile and sequencing of the pulsescan be initially programmed by the information being downloaded from theuser interface/host controller 150 to the dedicated MFC controller 180.The downloaded profile and sequencing allows the MFC to carry out all ofthe sequencing steps in response to a single trigger signal from theinterface/controller 150. Using a dedicated MFC 160, the dedicatedcontroller can be configured and arranged so as to carry out all of thesequencing steps in a well controlled and timely manner, freeing thehost controller/interface to carry out all of its other functionswithout interfering with the pulse gas delivery.

The PGD mode provides operational steps for three delivery types ofpulse gas delivery processes—time based delivery, mole based delivery,and profile based delivery providing a further advantage over thepressure based gas pulse delivery devices. In the time based pulsedelivery process, the user is required to configure and arrange thededicated MFC controller 180 with the following parameters for theprocess that is to be controlled: (1) at least one targeted flow setpoint (Q_(sp)), (2) at least one time length of the pulse-on period(T_(on)), (3) at least one time length of the pulse-off period(T_(off)), and (4) the total number of pulses (N) required to completethe process.

As shown in FIG. 4, the parameters are configured or downloaded from thehost controller to the dedicated MFC controller of the MFC so that theMFC controller controls the pulse delivery as a function of theseparameters. When the pulse gas delivery sequence is to be delivered, thehost computer simply provides a trigger signal to the MFC, and the MFCcarries out the sequence of pulses. As shown in FIG. 4, once the MFC 160receives the trigger signal from the host controller 150 to startdelivery, the MFC 160 controls the PGD process according to the recipeby turning the MFC on (controlling the flow to the targeted flow setpoint by regulating the openness of the valve) and off (controlling theflow to zero by closing the valve) based on the prescribed pulse onperiod and the pulse off period for each pulse period. This results invery good control of the sequencing, timing and duration of the pulses.

For mole based pulse delivery, a user specifies the followingparameters: (1) mole delivery set point (n_(sp)), (2) the targeted timelength of the pulse-on period (T_(on)), (3) the targeted time length ofthe pulse-off period (T_(off)), and (4) the number of pulses (N). Basedon this information, the dedicated controller 180 of MFC 160 isconfigured and arranged so as to automatically adjust the flow set pointto precisely deliver within the targeted pulse-on period the targetedmole amount of gas based on measurements taken by a flow sensor 170,according to the following equation:

$\begin{matrix}{{\Delta \; n} = {\int_{t\; 1}^{t\; 2}{Q \cdot {dt}}}} & (1)\end{matrix}$

wherein Δn is the number of moles of gas delivered during the pulse-onperiod (between times t1 and t2); and

Q is the flow rate measured by sensor 170 of the MFC 160 during thepulse-on period.

Thus, using the mole based pulse delivery mode, the MFC controls, andadjusts as necessary, the flow set point so as to control the number ofmoles delivered with each pulse. Based on these parameters, the MFC 160automatically delivers N pulses of flow in a precise timing sequence,with each pulse delivering Δn moles during the portion of each pulse onperiod (T_(on)) that the MFC is on, and turning the MFC off for thepulse off period (T_(off)). During operation of the mole based pulsedelivery operation, the MFC 160 will automatically adjust the flow setpoint (Q_(sp)) based on the calculated mole amount of gas delivered ofEq. (1) using the flow sensor measurement (Q) in order to preciselydeliver the desired number of moles within the targeted pulse-on period(T_(on)) for each pulse.

Mole based delivery is preferred (but not required) when multipleprocess tools are being used, or flow to different parts or devices of aprocess tool are required to be matched. In such a case multiple highperformance MFCs are used to provide flow through the correspondingmultiple delivery channels. To ensure that mole delivery is accurate,each MFC 160 uses feedback control loop from its flow sensor 170 tocontrol its valve 190. Thus, when multiple delivery channels are used,there may be variations in response time, valve conductance, etc. Insuch a case mole based pulse delivery can be used to ensure that theamount (moles) of gas delivered with each pulse in each delivery channelis the same, regardless of these factors, since mole delivery will beindependent of these factors. In one embodiment, feedback is used tocorrect the errors in the amount of gas delivered caused by valveresponse times.

It is contemplated that other parameters or other combinations ofparameters may be used to control gas delivery. For example, for timebased delivery an off flow set point can be entered for delivery of gasduring the T_(off) period, instead of defaulting to zero.

Repeatability and accuracy are improved by both time based and molebased delivery method using the dedicated controller of a MFC becausethe PGD control responsibility has been taken away from the hostcontroller 150 (reducing delays due to work load) and because the signaltransmission is closer to (and in fact within) the MFC 160 (reducingcommunication jitter), and the MFC itself is optimized for pulse gasdelivery.

Finally, the third mode of operation is the profile pulse mode. In oneembodiment of the profile pulse type of delivery, a user creates aprofile characterizing one or more pulses. For each pulse in theprofile, the user specifies the flow set point and the corresponding onand off pulse period, i.e., (1) the flow set point Q_(sp1) and acorresponding first pulse on and off period (T_(on1) T_(off1)), (2) theflow set point Q_(sp2) and a corresponding second pulse on and offperiod (T_(on2) T_(off2)), . . . (m) the flow set point Q_(spm) and acorresponding m-th pulse on and off period (T_(onm) T_(offm)), etc.Thus, a set of parameters are provided for each pulse of the entire setof pulses, allowing the pulses to vary depending on the type of processbeing run. FIGS. 5A and 5B illustrate two examples of sets of pulseprofiles. While in some embodiments, a user can define an ordinaryon/off pulse with varying set points during T_(on) (as seen in FIG. 5A),in other embodiments, the user may enter more than one flow set pointfor both the on period and off period such that a stair-step typeprofile can be created as seen in FIG. 5B. The latter is possiblebecause the MFC employs a proportional control valve. Unlike ashutoff/on valve, the proportional control valve can be set at anyposition between a totally open position and a totally closed position,providing a further advantage over the pressure based PGD device, suchas the one shown in FIG. 1. In the profile pulse delivery mode, the usercan also specify the mole delivery set point (n_(spi)) instead of theflow set point Q_(spi) along with the corresponding pulse on and offperiod (T_(oni) T_(offi)) for each of the pulses in the profile recipe.

Thus, the MFC 160, and not the host controller 150, coordinates theopening and closings operation of the control valve 190 and,accordingly, gas delivery. Historically, MFCs were analog devicesincapable of accurately performing such PDG control responsibilitieswith such relatively short pulses. Newer, digital MFCs, however, arecapable of taking on the responsibility of controlling the proportionalcontrol valve of the MFC. Given the aforementioned need for faster PGDprocesses, higher repeatability and accuracy is achieved using thededicated MFC controller 180 to run the PGD delivery process than wouldotherwise be possible. Instead of the host controller having to sendsignals to turn on and off the MFC, the process functions are carriedout alone by the MFC 160 of FIG. 3, eliminating a significant amount ofhardware while assuring more accurate delivery. The required controlrecipe parameters vary based on the type of PGD mode being used, asdescribed in more detail below. The host controller 150 may also send anabort signal to the MFC controller 180 at any time to abort pulse gasdelivery. For example, if a safety check fails, the host controller 150may demand the MFC 160 to immediately stop triggered gas deliverysequencing that is in process. Similarly, if the host controller 150detects that incorrect gas delivery is being performed, then the hostcontroller 150 may send an abort signal. In this way the host computer150 can continue to monitor other processes, while the gas deliverysteps are dedicated to the dedicated controller 180 of MFC 160.

In various embodiments of the present disclosure, a host controller 150can be used in conjunction with a plurality of MFCs 160 used with acorresponding number of delivery channels as mentioned above. The hostcontroller 150 sends timely trigger signals to each MFC 160. The hostcontroller 150, thus, can offset trigger signals to sequentially orsimultaneously trigger the plurality of MFCs 160. In this configuration,the host controller 150 may stagger the trigger signals so that thedelivery channels do not deliver gas simultaneously. For example,suppose control parameters define a T_(on) of 0.25 s and T_(off) of 0.75s in each of two MFCs 160. If the host controller 150 sends a triggersignal to the second MFC 0.5 s after triggering the first MFC, then theprocess tool 200 will receive delivery of gas equivalent to a T_(on) of0.25 s and T_(off) of 0.25 s (if the two gas chambers are filled withthe same gas).

Test results using the disclosed approach indicated an improvement inthe repeatability error over the experimental approach using a hostcomputer to control the process by two orders of magnitude.

Embodiments incorporating further improvements are illustrated in FIGS.6-9. As shown in FIG. 6, a high performance MFC 220 can include one ormore interfaces 230 which can be configured to provide communicationports capable of receiving both at least one digital signal input asshown at 240, and at least one analog signal input 250; and at least onedigital signal output as shown at 310, and at least one analog signaloutput 300. In such an arrangement, for example, a recipe can bedownloaded to the MFC memory 260 through the digital input 240 of theinterface, and the trigger signal can be provided through the analoginput 240 of the interface to start the MFC delivery gas in accordancewith the stored recipe. The processor/controller 270 receives signalsfrom the flow sensor 280 of the MFC and controls the control valve 290according to the recipe and the sensed flow. The one or more interfaces230 can also be configured to include at least one analog signal output300 and digital signal output 310. These outputs can be used for exampleas signals provided to other devices or tools.

With the configuration shown, the illustrated embodiment of the massflow controller (MFC) 220 is thus a programmable MFC, including at leastan input (such as the analog signal input shown at 250) configured toreceive an input signal, an output (such as analog signal output 300 ordigital signal output 310) configured to provide an output signal, and acommunication port (such as digital signal input 240) configured toreceive program instructions including instructions for the programmedor operational configuration of the MFC 220, and programming data usedby the MFC. MFC 220 also includes flow sensor 280 configured to sensethe flow of gas through the mass flow controller, a control valve 290configured to control the flow of gas though the mass flow controllerand memory 260 configured and arranged to receive programming dataincluding data determining the programmed configuration of the mass flowcontroller as either a digital or analog configuration for trigging thegas delivery. The processor/controller 270 operates the mass flowcontroller 220 in accordance with the programmed configuration. When thesystem configuration is programmed as a digital configuration, theprogrammed digital configuration enables the mass flow controller torespond to digital signals applied to the input 240. Alternatively, whenthe system configuration is programmed as an analog configuration, theprogrammed analog configuration enables the mass flow controller torespond to analog signals applied to the input 250.

The input configured as a communication port in the illustratedembodiment is also configured to receive data relating to parametersassociated with at least one of two modes of operation of the mass flowcontroller. The modes of operation of the mass flow controller caninclude a classic mass flow controller mode of operation, wherein theinput signal represents the set point setting for operating the MFC inthe classic mass flow controller mode of operation. The other mode ofoperation can include a pulse gas delivery mode of operation, whereinthe input signal represents a pulse trigger signal for operating the MFCso as to deliver a sequence of pulses in the pulse gas delivery mode ofoperation. Thus, the communication port is configured to receiveparameters for pulse gas delivery. The parameters can be associated witha mole delivery mode of gas pulse delivery operation. The parameters canalso include the pulse-on period, pulse-off period, the mole deliveryset point, and the number of pulses.

The illustrated embodiment of the communication interface 230 thusincludes the digital communication port, an analog input or pin forforming an input arranged to receive an analog trigger signal input, andan analog output or pin configured to form the output for providing ananalog signal output. The analog signal output can be used tosynchronize the operation of the MFC with the operation of anotherdevice or tool. This is particularly useful where two devices eachprovide a sequence of pulses (which can be the same or differentsequence) which must be synchronized with each other, or the two deviceseach provide a pulse synchronized with the pulse of the other device.For example, as shown in FIG. 7, the other device can be, for example,another high performance MFC and/or a RF generator and/or a pressurecontroller. This enables the synchronization of the various tool deviceswhen they are being used to simultaneously carry out parallel steps fora common process or different processes.

As shown in FIG. 7, a host computer at 350 can download the pulsesequences to each of the MFCs 360 over the digital communication bus370. In the illustrated embodiment, the outputs of the MFCs areconnected in a successive daisy chain arrangement, and each outputsignal 380 can also be split and re-routed to provide to other deviceson a process tool, such as a RF generator, a plasma generator or apressure controller, and/or in other embodiments to tool devices ondifferent process tools. In an exemplary embodiment, when the processbegins, a trigger signal is sent to the first MFC 360 a. The first MFC360 a delivers a sequence of pulses in accordance with the sequenceprogrammed in its memory. At a certain prescribed time, thesynchronization output of the first MFC 360 a is provided as a triggersignal input to the second MFC 360 b as well as to the tool device of,for example, a RF generator, The sequence proceeds with each successiveMFC 360. Each trigger signal thus synchronizes the operation of one MFCwith the next MFC in the daisy chain arrangement of any number of MFCs(generally indicated in FIG. 7 by N). The synchronization signal of oneMFC can be generated prior to the completion of the delivery of thesequence of pulses by the MFC. Alternatively, the synchronization signalcan be generated simultaneously with the completion of the delivery ofthe sequence of pulses, or the synchronization signal can be generatedafter the completion of the delivery of the sequence of pulses by apredetermined delay. It should be noted that the pulse trigger signalcan be a digital or an analog signal. In one embodiment the outputsignal is a TTL synchronization output signal for use by another device.

Referring still to FIG. 7, the illustrated system embodiment shown canoperate as a multi-channel gas delivery system including a plurality Nof flow channels 380, each channel comprising a mass flow controller 360configured to control the flow of gas through the corresponding channel.In the illustrated arrangement, each MFC can be arranged to provide atleast one pulse of gas, with the MFCs being connected in series (a daisychain arrangement). In this way each MFC can provide the same ordifferent gases to the tool, each as a pulse of a prescribed duration asbest seen in FIG. 8. Further, the quantity (e.g., mass) of gas of eachdelivered pulse can vary from channel to the channel.

As shown in FIG. 8, in this embodiment the MFCs 360 can be synchronizedto simultaneously deliver each pulse when the previous pulse ends. Asnoted above, each successive pulse can be delayed relative to theprevious pulse, or commence prior to the end of the previous pulse, orsome combination of any two or all three synchronization arrangements.

As described above, the digital communication port of each mass flowcontroller can be configured to receive data relating to parametersassociated with at least one of two modes of operation of the mass flowcontroller. The MFC can be configured to operate in a classic mode ofgas delivery operation, or pulse mode of gas delivery operation. Asshown in FIG. 9, when an input trigger is received at step 400, if theMFC is configured to operate in the classic mass flow controller mode at402 it proceeds to step 404 and delivers a prescribed amount of gas bysensing the actual flow with the sensor, and controlling the controlvalve based on the sensed flow and the received flow setpoint. The MFCthen proceeds to the step 406 and provides an output signal for the nextMFC, or if functioning alone or if the last MFC in the chain, theprocess ends. Similarly, if operating in the pulse mode the processproceeds from step 402 to 408 to deliver the prescribed amount of gas inpulses. The process then proceeds to step 406.

When operating in a pulse mode delivery, the parameters can beassociated with a mole delivery mode of gas pulse delivery operation. Insuch a configuration, the parameters include the pulse-on period,pulse-off period, the mole delivery setpoint, and the number of pulses.

As described, the gas delivery system reliably measures the amount ofmaterial (mass) flowing into the semiconductor tool, and provides foraccurate delivery of the mass of a gas in pulses of relatively shortduration in a reliable and repeatable fashion. Further, the systememploys a more simplified operation, while providing delivery of thedesired number of moles of gas over a wide range of values, without theneed to divert gas to achieve the accurate, reliable and repeatableresults.

The components, steps, features, objects, benefits and advantages whichhave been discussed are merely illustrative. None of them, nor thediscussions relating to them, are intended to limit the scope ofprotection in any way. Numerous other embodiments are also contemplated.These include embodiments which have fewer, additional, and/or differentcomponents, steps, features, objects, benefits and advantages. Thesealso include embodiments in which the components and/or steps arearranged and/or ordered differently.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications which are set forth in thisspecification, including in the claims which follow, are approximate,not exact. They are intended to have a reasonable range which isconsistent with the functions to which they relate and with what iscustomary in the art to which they pertain.

All articles, patents, patent applications, and other publications whichhave been cited in this disclosure are hereby incorporated herein byreference.

The phrase “means for” when used in a claim is intended to and should beinterpreted to embrace the corresponding structures and materials whichhave been described and their equivalents. Similarly, the phrase “stepfor” when used in a claim is intended to and should be interpreted toembrace the corresponding acts which have been described and theirequivalents. The absence of these phrases in a claim mean that the claimis not intended to and should not be interpreted to be limited to any ofthe corresponding structures, materials, or acts or to theirequivalents.

Nothing which has been stated or illustrated is intended or should beinterpreted to cause a dedication of any component, step, feature,object, benefit, advantage, or equivalent to the public, regardless ofwhether it is recited in the claims.

The scope of protection is limited solely by the claims which nowfollow. That scope is intended and should be interpreted to be as broadas is consistent with the ordinary meaning of the language which is usedin the claims when interpreted in light of this specification and theprosecution history which follows and to encompass all structural andfunctional equivalents.

Reference is made to U.S. patent application Ser. No. 13/344,387,entitled SYSTEM FOR AND METHOD OF FAST PULSE GAS DELIVERY, filed Jan. 5,2012 in the names of Junhua Ding, Michael L′Bassi and Tseng-Chung Leeand assigned to the present assignee; U.S. patent application Ser. No.12/893,554, entitled SYSTEM FOR AND METHOD OF FAST PULSE GAS DELIVERY,filed Sep. 29, 2010 in the name of Junhua Ding, and assigned to thepresent assignee, now U.S. Pat. No. 8,997,686, issued Apr. 7, 2015; U.S.patent application Ser. No. 13/035,534, entitled METHOD AND APPARATUSFOR MULTIPLE-CHANNEL PULSE GAS DELIVERY SYSTEM, filed Feb. 25, 2011 inthe name of Junhua Ding and assigned to the present assignee, now U.S.Pat. No. 9,348,339, issued May 24, 2016, and U.S. patent applicationSer. No. 13/193,393, which is now abandoned, entitled Systems andMethods of Controlling Time-Multiplexed Deep Reactive-Ion EtchingProcesses, filed Jul. 28, 2011 in the name of Vladislav Davidkovich etal. and assigned to the present assignee. The entire teachings of theabove applications are incorporated herein by reference.

What is claimed is:
 1. A system comprising: a multi-channel gas deliverysystem including a plurality of flow channels, each channel comprising amass flow controller configured to control the flow of gas through thecorresponding channel and including: an input configured to receive aninput signal; an output configured to provide an output signal; acommunication port configured to receive program instructions includinginstructions on the operational configuration of each mass flowcontroller; a flow sensor configured to sense the flow of gas throughthe mass flow controller of the corresponding channel; a control valveconfigured to control the flow of gas though the mass flow controller ofthe corresponding channel; memory configured and arranged to receiveprogramming data determining the programmed configuration of the massflow controller as either a digital or analog configuration; and aprocessor/controller for operating the mass flow controller inaccordance with the programmed configuration; wherein the input signalto the mass flow controller initiates the operation of the mass flowcontroller to deliver a prescribed amount of gas, and the output signalis generated as a function of the timing of the delivery so that theoutput signal can be used to synchronize each mass flow controller to atleast one other device.
 2. A system according to claim 1, wherein theoutput signal of at least one mass flow controller is used as an inputsignal to initiate the operation of another one of the mass flowcontrollers of the multi-channel fast pulse gas delivery system todeliver a prescribed amount of gas so that the mass flow controllersdefine a daisy chain of devices sequentially providing the delivery ofprescribed amounts of gas through the corresponding channels.
 3. Asystem according to claim 1, wherein the output signal of each of themass flow controllers is used to provide control signals applied to anRF power generator.
 4. A system according to claim 1, wherein the outputsignal of each of the mass flow controllers is used to provide controlsignals applied to a pressure controller.
 5. A system according to claim1, wherein the input and output signals are analog signals.
 6. A systemaccording to claim 1, wherein the digital communication port of eachmass flow controller is configured to receive data relating toparameters associated with at least one of two modes of operation of themass flow controller.
 7. A system according to claim 6, wherein the atleast one of two modes of operation of each mass flow controllerincludes a pulse gas delivery mode of operation, wherein the inputsignal represents a pulse trigger signal for operating the MFC so as todeliver a sequence of pulses in the pulse gas delivery mode ofoperation.
 8. A system according to claim 6, wherein the digitalcommunication port is configured to receive parameters for pulse gasdelivery.
 9. A system according to claim 8, wherein the parameters areassociated with a mole delivery mode of gas pulse delivery operation.10. A system according to claim 9, wherein the parameters include thepulse-on period, pulse-off period, the mole delivery setpoint, and thenumber of pulses.
 11. A system according to claim 6, further including adigital communication interface that includes the digital communicationport.
 12. A system according to claim 6, further including both adigital communication interface and an analog communication interface.13. A system according to claim 6, further including an analogcommunication interface having an analog input pin for forming the inputand receiving an analog trigger signal input, and an analog output pinfor forming the output and providing an analog synchronization signaloutput.
 14. A system according to claim 13, wherein the analogsynchronization signal is generated prior to the completion of thedelivery of the sequence of pulses.
 15. A system according to claim 13,wherein the analog synchronization signal is generated simultaneouslywith the completion of the delivery of the sequence of pulses.
 16. Asystem according to claim 13, wherein the analog synchronization signalis generated after the completion of the delivery of the sequence ofpulses by a predetermined delay.
 17. A system according to claim 6,wherein the output signal is a TTL synchronization output signal for useby another device.
 18. A method of operating a mass flow controller ofthe type comprising at least one communication port, the methodcomprising: receiving, at the communication port, program instructionsincluding instructions relating to the operational configuration of themass flow controller as responsive to either digital or analog inputsignals; and operating the mass flow controller in accordance with theprogrammed configuration.
 19. A method of operating a mass flowcontroller according to claim 18, wherein a programmed digitaloperational configuration enables the mass flow controller to respond todigital signals applied to the input.
 20. A method of operating a massflow controller according to claim 18, wherein a programmed analogoperational configuration enables the mass flow controller to respond toanalog signals applied to the input.
 21. A method of operating a massflow controller according to claim 18, wherein receiving at thecommunication port program instructions includes receiving data relatingto parameters associated with at least one of two modes of operation ofthe mass flow controller.
 22. A method of operating a mass flowcontroller according to claim 21, wherein at least one of two modes ofoperation of the mass flow controller includes a classic mass flowcontroller mode of operation, and the input signal represents the setpoint setting for operating the MFC in the classic mass flow controllermode of operation.
 23. A method of operating a mass flow controlleraccording to claim 21, wherein at least one of two modes of operation ofthe mass flow controller includes a pulse gas delivery mode ofoperation, and further delivering a sequence of pulses in the pulse gasdelivery mode of operation in response to an input signal.
 24. A methodof operating a mass flow controller according to 23, wherein receivinginstructions at the communication port program includes receivingparameters for pulse gas delivery.
 25. A method of operating a mass flowcontroller according to claim 24, wherein the parameters for pulse gasdelivery are associated with a mole delivery mode of gas pulse deliveryoperation.
 26. A method of operating a mass flow controller according toclaim 25, wherein the parameters include the pulse-on period, pulse-offperiod, the mole delivery setpoint, and the number of pulses.
 27. Amethod of operating a mass flow controller according to claim 23,further including receiving an analog trigger signal input at an analoginput pin of an analog communication interface and providing an analogsynchronization signal output at an analog output pin of the analogcommunication interface.
 28. A method of operating a mass flowcontroller according to claim 23, further including generating an outputsignal representing a synchronization signal for use in synchronizingthe timing of the delivery of a sequence of pulses with the operation ofanother device.
 29. A method of operating a mass flow controlleraccording to claim 28, wherein the another device is a second mass flowcontroller.
 30. A method of operating a mass flow controller accordingto claim 29, wherein the synchronization signal is a trigger signal foruse as an input to the second mass flow controller.
 31. A method ofoperating a mass flow controller according to claim 28, wherein theanother device is an RF power generator.
 32. A method of operating amass flow controller according to claim 28, wherein the another deviceis a pressure controller.
 33. A method of operating a mass flowcontroller according to claim 30, further including generating thesynchronization signal prior to the completion of the delivery of thesequence of pulses.
 34. A method of operating a mass flow controlleraccording to claim 30, further including generating the synchronizationsignal simultaneously with the completion of the delivery of thesequence of pulses.
 35. A method of operating a mass flow controlleraccording to claim 30, further including generating the synchronizationsignal by a predetermined delay after the completion of the delivery ofthe sequence of pulses.
 36. A method of operating a mass flow controlleraccording to claim 30, wherein the trigger signal is generated as adigital signal.
 37. A method of operating a mass flow controlleraccording to claim 30, wherein the trigger signal is generated as ananalog signal.
 38. A method of operating a mass flow controlleraccording to claim 28, wherein the output signal is a TTLsynchronization output signal for use by another device.
 39. A method ofoperating a multi-channel gas delivery system including a plurality offlow channels, each channel comprising a mass flow controller configuredto control the flow of gas through the corresponding channel, the methodcomprising: providing an input signal to one of the mass flowcontrollers so as to initiate the operation of the mass flow controllerto deliver a prescribed amount of gas; generating an output signal fromthe mass flow controller as a function of the timing of the delivery ofthe prescribed amount of gas so that the output signal can be used tosynchronize each mass flow controller to at least one other device;receiving program instructions at a communication port includinginstructions on the operational configuration of each mass flowcontroller; determining the programmed configuration of the mass flowcontroller as either a digital or analog configuration as a function ofthe received instructions; and operating the mass flow controller inaccordance with the programmed configuration; wherein the input signalto the mass flow controller initiates the operation of the mass flowcontroller to deliver a prescribed amount of gas, and the output signalis generated as a function of the timing of the delivery so that theoutput signal can be used to synchronize each mass flow controller to atleast one other device.
 40. A method of operating a multi-channel gasdelivery system according to claim 39, further including using theoutput signal of at least one mass flow controller as an input signal toinitiate the operation of another one of the mass flow controllers ofthe multi-channel fast pulse gas delivery system to deliver a prescribedamount of gas so that the mass flow controllers define a daisy chain ofdevices sequentially providing the delivery of prescribed amounts of gasthrough the corresponding channels.
 41. A method of operating amulti-channel gas delivery system according to claim 39, furtherincluding applying the output signal of each of the mass flowcontrollers as a control signal to an RF power generator.
 42. A methodof operating a multi-channel gas delivery system according to claim 39,further including applying the output signal of each of the mass flowcontrollers as a control signal to a pressure controller.
 43. A methodof operating a multi-channel gas delivery system according to claim 39,wherein the input and output signals are analog signals.
 44. A method ofoperating a multi-channel gas delivery system according to claim 39,further including receiving at a digital communication port of each massflow controller data relating to parameters associated with at least oneof two modes of operation of each such mass flow controller.
 45. Amethod of operating a multi-channel gas delivery system according toclaim 44, wherein the at least one of two modes of operation of eachmass flow controller includes a pulse gas delivery mode of operation,wherein the input signal represents a pulse trigger signal for operatingthe MFC so as to deliver a sequence of pulses in the pulse gas deliverymode of operation.
 46. A method of operating a multi-channel gasdelivery system according to 44, wherein receiving at a digitalcommunication port of each mass flow controller data relating toparameters associated with at least one of two modes of operation ofeach such mass flow controller includes receiving parameters for pulsegas delivery.
 47. A method of operating a multi-channel gas deliverysystem according to claim 46, wherein receiving at a digitalcommunication port of each mass flow controller data relating toparameters associated with at least one of two modes of operation ofeach such mass flow controller includes receiving parameters associatedwith a mole delivery mode of gas pulse delivery operation.
 48. A methodof operating a multi-channel gas delivery system according to claim 47,wherein the parameters include the pulse-on period, pulse-off period,the mole delivery setpoint, and the number of pulses.
 49. A method ofoperating a multi-channel gas delivery system according to claim 48,wherein the output signal of each mass flow controller is an analogsynchronization signal, and further including generating the analogsynchronization signal prior to the completion of the delivery of thesequence of pulses by the mass flow controller.
 50. A method ofoperating a multi-channel gas delivery system according to claim 49,wherein the analog synchronization signal is generated simultaneouslywith the completion of the delivery of the sequence of pulses.
 51. Amethod of operating a multi-channel gas delivery system according toclaim 49, wherein the analog synchronization signal is generated afterthe completion of the delivery of the sequence of pulses by apredetermined delay.
 52. A method of operating a multi-channel gasdelivery system according to claim 48, wherein the output signal of eachmass flow controller is a TTL synchronization output signal for use byanother device.